SQ : Collective Traits (Ex): A collective creature can move through squares occupied by enemies and vice versa without impediment,although the collective creature provokes an attack of opportunityif it does so. A collective creature can move through cracks or holes large enough for its component creatures. Moving through small openings is a full–round action that provokes an attack of opportunity and the collective creature’s speed is reduced to 5 feet (1 square) until it is clear of the obstruction.SQ : Glide (Ex)

Defensive Abilities:

Damage Reduction (Su): A collective creature gains damage reduction based on its Hit Dice: 5 HD or less, damage reduction 5/ bludgeoning; 6–11 HD, damage reduction 10/bludgeoning; 12 HD or more, damage reduction 15/bludgeoning.
One from Many (Ex): A collective creature has no clear front or back and no discernable anatomy, so it is not subject to critical hits or flanking. Reducing a collective creature to 0 hit points or lower causes it to break apart into its component creatures. Collective creatures are never staggered or reduced to a dying state by damage. At will, a collective can break into its component swarms or even into individual creatures and disperse

Immunities (Ex): A collective creature is immune to any spell or effect that targets a specific number of creatures (including singletarget spells such as disintegrate), with the exception of mindaffecting effects (charms, compulsions, phantasms, patterns, and morale effects). A collective creature rendered unconscious by means of nonlethal damage becomes disorganized and dispersed, and does not reform until its hit points exceed its nonlethal damage
Weaknesses: A collective creature takes half again as much (+50%) damage from spells or effects that affect an area, such as splash weapons and evocation spells such as fireball.
Special Attacks:

Engulf (Ex): A collective creature can occupy the same square(s) as a creature that fits within its space as a standard action (since the individuals can crawl all over the opponent). It cannot make any other attack in any round in which it engulfs. The collective creature merely has to move over its opponents, affecting as many as it can cover. Opponents can make attacks of opportunity against the collective creature, but if they do so, they are not entitled to a saving throw. Those who do not attempt attacks of opportunity must succeed on a Reflex save or be engulfed; on a success, they are pushed back or aside (opponent’s choice). Engulfed creatures take slam damage and are subjected to any other special attack the collective might have (poison, disease, and so on) each round on the collective’s turn. An engulfed creature is considered to be grappled and trapped within the collective creature’s body.
Many from One (Ex): A collective creature can sling a clump of individuals from its body at a single target within 10 feet (with a 10-foot range increment). This requires a successful ranged touch attack. If struck, the target takes 1d6 points of damage. If the base swarm’s normal attack deals disease, poison, or any other such damage, its ranged attack does as well. If the attack allows a save to avoid or resist, the target can attempt a saving throw. A collective creature automatically takes 1 point of damage each time it uses this attack since the individual components of itself used in the attack are either killed or scurry away.
Swarming Body (Ex): Any creature attacking a collective creature unarmed or with natural weapons automatically takes 1d4 points of damage as the swarms comprising the collective creature bite, sting or otherwise attack the opponent. Large collectives deal 1d6 points of damage; Huge collectives deal 1d8 points of damage with their swarming body attack.